Embolic coils can be used to treat a number of medical conditions. For example, embolic coils may be used to stop undesired blood flow or to treat vascular malformations or structural defects, as in, for example, the treatment of aneurysms, arteriovenous malformations, and/or traumatic fistulae. In addition, embolic coils can be used to reduce or stop the blood flow to tissues or organs to treat conditions such as tumors or hemorrhages.
Embolic coils are typically introduced into a blood vessel by using a microcatheter that extends from a proximal point outside the patient's body to a distal point near the embolization site. An introducer sheath containing the coil can be used to carry and protect the coil prior to insertion into the patient. Further, the introducer sheath may be used to transfer the coil to the microcatheter and/or to assist in deploying the coil at a selected embolization site.
However, some introducer sheaths are not optimized for successful coil delivery. For example, many sheaths are straight extrusions having a diameter sized to mate with the proximal hub of a microcatheter. Consequently, in order to match the small dimensions of microcatheters, many sheaths have thin walls that can buckle easily under compression, which can lead to premature detachment of the coils and/or make it difficult to advance the coil from the introducer sheath into the microcatheter. If this occurs, the physician may need to remove the microcatheter, potentially wasting time spent in securing access to the selected embolization site.
In addition, retrograde blood flow into the sheath can be a problem. For example, blood flow into the introducer sheath can cause premature thrombosis of some embolic coils, thereby preventing delivery into the microcatheter.
The present disclosure is directed at overcoming one or more of the short-comings of introducer sheaths as set forth above.